Preliminary studies performed by applicant indicate that the fertile period in women can be defined by monitoring electrical characteristics of saliva and cervical mucus. Previous investigators have shown that electrolyte constituents of these fluids change cyclically in relation to concentrations of reproductive hormones in women. More data are needed to validate the method. A probable physiological rationale for observed changes in salivary electrical resistance (SER) and vaginal electrical resistance (VER) and their relationship to the menstrual cycle has been generated and will be tested. In this study, fifty women will record daily measurements of SER and VER using a specially designed instrument. Basal Body Temperature (BBT) will be recorded, but will not be used to define the time of ovulation. Ovulation will be diagnosed by luteinizing hormone (LH) assay and, where appropriate, by ultrasound scan as well. Statistical evaluation of the correlation of the electrical measurements with ovulation will be performed. If successful, this research will result in a very useful tool for the management of infertility in the near future. Later, it is expected that the instrument will also be used to aid natural family planning.